Housing authorities in Weifang, Shandong Province are investigating an alleged construction scandal after a recent media report revealed illegal, substandard materials were used to make concrete that was poured into apartment buildings.

The China Central Television (CCTV) investigative program Topics in Focus on Wednesday reported that some construction contractors in Weifang were using an aggregate made from ground up rock, instead of high-quality, more expensive sand to make concrete. A developer told the reporter that "Chinese are not afraid of risks" when asked if using ground up rock in place of sand, which costs twice as much, posed long term safety concerns for residents.

The CCTV report said several factories and construction sites in Anqiu and Changle counties were found to be processing and selling the ground rock. Three of the factories have been suspended from operating after the Weifang housing authority conducted onsite inspections, Xinhua reported.

A local housing authority official, however, told the Global Times that an investigation failed to turn up any illegal practices. "We conducted an urgent inspection countywide today but failed to find the source of the illegal sand business, and no construction sites are using it," said a spokeswoman with the work safety office under the Changle housing authority who spoke on condition her name was withheld.

While the Weifang Construction Quality and Safety Supervision Station banned substandard sand and poor quality concrete in 2011, the CCTV report showed "bad sand" being sold at some construction markets in the city that are not inspected by the government.

The Weifang-based news portal wfnews.com.cn reported in June 2011 that some cement plants in Changle's Yingqiu township were found to be producing and selling ground up rock as construction sand. Local villagers said the concrete broke easily and they wouldn't use it to build a doghouse or pigpen, the report said.

In 2010 some companies in Changle were involved in the substandard sand washing business, and the authority issued a regulation banning the trade and use of substandard sand in construction, said the housing authority official.

She said the commission has not received any recent reports of illegal aggregate being used to make concrete but the authority will conduct more frequent inspections after the winter when construction on housing projects resumes.

The Weifang city Commission of Housing and Urban-Rural Development was not available for comment as of press times Thursday.

An experiment conducted by the construction material lab with Tsinghua University showed that concrete made from substandard aggregate has 20 percent less strength than concrete made from quality sand.